The present invention relates to a lubricant recovery device. For example, the present invention relates to a device in a spindle device of a machine tool having a vertical main spindle. This device recovers lubricant which is supplied together with carrier air to one side of a bearing rotatably supporting a main spindle in a fixed housing.
For example, a bearing that rotatably supports a main spindle such as a machining center in a fixed housing has a high dn value in order to satisfy a demand for enhancement of a rotational speed of the main spindle. As a method for lubricating the bearing, therefore, oil air lubrication or oil mist lubrication is frequently adopted in place of grease lubrication. Specifically, lubricant which is relatively low in viscosity is supplied from an external source to one side of the bearing through use of carrier air. The oil air lubrication and the oil mist lubrication are superior to the grease lubrication in the following point. That is, since new lubricant is constantly supplied from the external source to the bearing, a rolling lifetime of the bearing does not depend on a lifetime of the lubricant.
In the case of adopting the oil air lubrication or the oil mist lubrication, however, the lubricant supplied to the bearing must be discharged.
As a conventional device for discharging lubricant supplied to a bearing, for example, JP-A-2001-090739 discloses a device having the following configuration. That is, a fixed housing has a through air channel that extends vertically, and an oil discharge passage. The oil discharge passage has a first end opened at an inner surface of the fixed housing on an opposite side to a lubricant supply side of a bearing, and a second end opened at an inner surface of the air channel. Herein, when air is fed from an upper opening of the air channel, lubricant is supplied to the bearing by means of flow of the air in the air channel and then is fed into the air channel through the oil discharge passage. Thereafter, the lubricant is discharged from a lower opening of the air channel in conjunction with the air flow.
In the case of using the device disclosed in JP-A-2001-090739, occasionally, the spent lubricant which is discharged from the lower opening of the air channel drops and adheres to a workpiece. For example, in a case where working is performed without using a cutting fluid, such as working for a mold assembly, if lubricant adheres to a workpiece, chips are attached to the workpiece due to the lubricant. Consequently, there is a possibility that a surface of the workpiece is damaged in finishing.
Moreover, JP-A-2002-018676 discloses a device having the following configuration. That is, a lubricant pan is provided at a bottom end surface of a fixed housing so as to receive lubricant discharged from a lower opening of an air channel. Moreover, a lubricant discharge pipe has a first end which is located in the lubricant pan, and a second end which extends to a lubricant discharge position. Further, an air pipe is provided for allowing air to pass therethrough. Herein, the lubricant discharge pipe and the air pipe are coupled to each other such that a flowing direction of the lubricant is equal to that of the air. When the air is supplied to the air pipe at high speed, the lubricant in the lubricant pan is discharged by suction.
In the case of using the device disclosed in JP-A-2002-018676, the lubricant pan, the lubricant discharge pipe, the air pipe and the like must be disposed around a tip end of a main spindle. In order to avoid interference with a workpiece, however, there is a possibility that the disposition of each component becomes considerably difficult.
Further, JP-A-2004-162872 discloses a device having the following configuration. That is, a housing has a carrier air discharge passage, a lubricant discharge passage and a dropping lubricant collecting passage. The carrier air discharge passage is formed for discharging carrier air from one side of a bearing. The lubricant discharge passage has a discharging air inlet and a discharging air outlet. The dropping lubricant collecting passage has an upper opening which communicates with the carrier air discharge passage and extends downward, and a lower opening which communicates with the lubricant discharge passage. Herein, a valve body is provided at a portion below the dropping lubricant collecting passage in the housing. The valve body moves between a first position and a second position such that the lower opening of the dropping lubricant collecting passage is opened and closed.
In the case of using the device disclosed in JP-A-2004-162872, working for the position where the valve body is provided, working for the lubricant discharging air inlet, and working for the lubricant discharging air outlet must be performed. Further, the device requires a larger number of constituent components.